Underwater sound source



Aug. 16, 1966 L. L. ROBINSON ET AL 7,

UNDERWATER SOUND SOURCE Filed April 6, 1962 6 Sheets-Sheet l INVENTORSLEONARD L. ROBINSON JOHN A. TREVETT BY K ng/1W4 %M ATTORNEYS.

L. L. ROBINSON ET AL UNDERWATER SOUND souncn Aug. 16, 1966 3,267,421

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Aug. 16, 1966 L. 1.. ROBINSON ETAL 3,267,421

UNDERWATER SOUND SOURCE 6 Sheets-Sheet 3 Filed April 6, 1962 INVENTORSAFZD L. ROBINSON A. TREVETT g- 1966 L. L. ROBINSON ET AL 3,267,421

UNDERWATER SOUND SOURCE 6 Sheets-Sheet 4 Filed April 6, 1962 NW \IPATTORNEYS.

Aug. 16, 1966 1.. L. ROBINSON ET AL 3,267,421

UNDERWATER SOUND SOURCE 6 Sheets-Sheet 5 Filed April 6, 1962 KUvmATTORNEYS.

Aug. 16, 1966 L. L. ROBINSON ET AL 3,267,421

UNDERWATER SOUND SOURCE Filed April 6, 1962 6 Sheets-Sheet e INVENTORSLEONARD L.ROBINSON JOHN A. TREVETT ATTORNEYS.

United States Patent 3,267,421 UNDERWATER SOUND SOURCE Leonard L.Robinson, Old Saybrook, and John A. Trevett, Old Lyme, Conn., assignorsto Textron Electronics, Inc., Providence, R.I., a corporation ofDelaware Filed Apr. 6, 1962, Ser. No. 185,648 6 Claims. (Cl. 340-12) Thepresent invention relates to underwater sound sources or generators.

Underwater sound sources can be divided into two basic categories inaccordance with the nature of the source of power, i.e., electroacousticand hydroacoustic. With both types, an electrical control signal isconverted into an acoustic output. Typical of the electroacousticdevices are those making use of the electromagnetic and piezoelectriceffects. In the hydroacoustic device the electric signal is used tocontrol a fluid valve which modulates the flow of hydraulic fluid toactuate an acoustic radiator. It is with the hydroacoustic device thatthe present invention is concerned.

As with all acoustic sources, efficiency in power conversion with highoutput power capability over a wide frequency range is a designobjective. At the same time, excessive weight and size is to be avoided.

The hydroacoustic device is capable of developing high power output atextremely low frequencies, say below 600 c.p.s. One such devi-ce isbased upon the principle of simultaneously driving a pair of opposedradiator pistons in opposite directions relative to a stationary housingin which they are sealed to alter the instantaneous volume of thehousing, thereby creating sound pressure in the surrounding medium.

For extremely large power output it becomes expedient to employindividual control valves with hydraulic amplification for each actuatorelement and to drive the plurality of valves in parallel. However, for alow power device the flow requirements are reduced and there no longeris a need for the greater flow capacity of multiple valving. Thus,strictly from a consideration of the flow requirements it would seempossible to use only a single valve to control a plurality of actuators.

Single valve control of multiple actuators implicitly requires that thehydraulic circuits of the actuators be freely interconnected. Since theactuator elements (and thereby the radiator pistons) must move in unisonfor proper acoustic operation this poses a serious problem.

For example, consider two pistons in a common cylinder with fluid underpressure being admitted between them. The piston which is subjected tothe smaller retarding force including load reaction, friction and soforth, will move to its end stop before the other piston moves at all.This type of out-of-phase operation can not be tolerated for faithfulnon-distorted acoustic reproduction.

The discovery of a way to overcome this seemingly incompatible situationforms the basis of the present invention. A sound source was constructedboth with a symmetrical hydraulic system between the actuator elementsassociated with the respective radiator pistons and with a strong springacting to bias each radiator piston to an intermediate position. Throughactual field tests it was discovered that the radiators did move inunison sufliciently so that the distortion remained at an acceptable lowlevel.

Therefore, in accordance with the present invention there is provided anunderwater sound source comprising a fluid tight housing having rigidwall portions including oppositely directed sound-radiating pistons, atleast two hydraulic actuator means within the housing coupledmechanically one to each of the pistons for imparting reciprocatorymotion thereto, means for obtaining hydraulic power, valving mechanismwithin the housing,

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duct means freely inter-coupling the actuator means in parallel and tothe means for obtaining hydraulic power through the valving mechanismfor operation under the control of the valving mechanism, the duct meansbetween the valving mechanism and the actuator means being dimensionedto provide for hydraulic symmetry between the actuator means coupledrespectively to one and the other of said pistons, spring means couplingeach of the pistons to stationary portions of the housing for biasingthe pistons toward an intermediate position, and means for controllingthe valving mechanism so as to cause reciprocation of the pistonssubstantially in unison alternately outwardly and inwardly relative tothe interior of the housing thereby varying the instantaneous volume ofthe housing.

A better understanding of the invention will be had after reading thefollowing detailed description with reference to the appended drawingsin which:

FIG. 1 shows the essential organization and relationship of parts of anunderwater sound source embodying the present invention, the fluid tighthousing being shown somewhat simplified and in longitudinal section withthe exception of the pistons of which only a portion is broken away, thepiston driving mechanism which includes a valve body, the valvingmechanism, the controlling means therefor, the duct means, and theactuator means being represented in simplified schematic form;

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1 and showingthe nature of the radiator piston;

FIG. 3 is a top plan view of an actual embodiment of gileGpilstondriving mechanism shown schematically in FIG. 4 is a bottom plan view ofthe driving mechanism shown in FIG. 3;

FIG. 5 is an elevational view of the left side of the driving mechanismshown in FIG. 3;

FIG. 6 is an elevational view of the right side of the driving mechanismshown in FIG. 3;

FIG. 7 is an elevational view of the front of the driving mechanismshown in FIG. 3;

FIG. 8 is an irregular sectional view to a slightly enlarged scale takengenerally along line 8-8 .of FIG. 3 with certain parts broken away forclearer representation;

FIG. 9 is a horizontal sectional view on the same scale as FIG. 8 takenalong line 9-9 of FIG. 5;

FIG. 10 is a fragmentary sectional view taken along line 10-10 of FIG.4;

FIG. 11 is a fragmentary sectional view taken along line 11-11 of FIG.4; and

FIG. 12 is a fragmentary sectional view taken along line 12-12 of FIG.4.

Reference should now be had to FIGS. 1 and 2. In this illustrativeexample it is assumed that the source of hydraulic power as well as thesource of control signals are external to the underwater sound source.The sound source is shown as consisting of .a cylindrical fluid tightmetal housing 10 having rigid wall portions including the oppositelydirected sound radiating pistons 11 and 12. The latter are characterizedby a ribbed construction to ensure lightness in weight with maximumrigidity.

A thick (e.g. /2") sheet of rubber or other strong waterproof elasticmaterial covers each piston 11 and 12 at 13 and 14, respectively, andextends beyond the pistons to overlap the stationary portion of thehousing. The sheets 13 and 14 are bonded as by an epoxy cement to theouter surface of the corresponding piston and are fastened as by screws15 to the housing 10. The junction with the housing must be watertight.

The pistons 11 and 12 are biased by the restraining action of theelastic sheets 13 and 14 so as to tend to assume the position seen inFIG. 2 in the corresponding openings 16 and 17 in the housing 10.

The actual mechanism for driving the pistons 11 and 12, due to itscomplexity, has been reduced to schematic form in FIG. 1 for conveniencein explaining its construction, operation, and basic principles. Whilethe ensuing discussion, therefore, will be confined to FIGS. 1 and 2,reference should be had to FIGS. 3 to 12 for the actual details ofconstruction. The same reference numerals appearing in FIGS. 1 and 2 areused throughout FIGS. 3 to 12 to designate corresponding parts. SinceFIGS. 1 and 2 represent only a simplified schematic, what appears as asingle element therein may involve a combination of several parts in theactual embodiment. In such case the several parts since they serve thesame purpose or function are designated by the same basic referencenumeral appearing in FIGS. 1 and 2, but are distinguished by smallletters of the alphabet. For example, in FIG. 1 a single passage or duct53 connects a port 45 in a cylinder 23 to a passage 57. In FIGS. 3 to 12(see particularly FIG. 12) the port 45 communicates with passage 53awhich connects with passage 53b which in turn, joins passage 57.

Where reference characters are shown in parenthesis they representeclipsed or hidden structure of identical construction.

The passages in the valve body to be described were introduced bydrilling or boring operations. These operations were carried out inknown manner from a face or other accessible surface of the body.Unwanted portions of the bores at the entrances to the body were thensuitably plugged. In order to facilitate reading of the drawings and toavoid repetitious description the small letter x has been usedthroughout FIGS. 3 to 12 after a reference numeral to indicate the pointof entry of the boring tool and the plug for a given passage designatedby the same numeral without the x. For example, 53ax is the pluggedentrance for drilled passage 53a (see FIG. 12).

Now, returning to FIGS. 1 and 2, the mechanism for driving the pistons11 and 12 is housed in a valve body 18. The piston 11 is coupled by rods19 and 20 to two hydraulic actuator means or elements within the housingin the form of identical rams 21 and 22 riding in identicalcorresponding cylinders 23 and 24 in body 18.

Identical rams 25 and 26 riding in identical cylinders 27 and 28 arecoupled by rods 29 and 30 to piston 12. It should be observed that withthe pistons in the neutral position with minimum stress of the elasticsheets the rams 21, 22, 25 and 26 are all located at the center orintermediate position of the respective cylinders. The actuatorelements, each consisting of a ram and cylinder, are of the rectilinearmotion type and impart reciprocatory motion to the radiators.

The present device requires a closed hydraulic system having a pressureline brought in through the connection 31 and a return line coupledthrough connection 32. The pressure line is shown symbolically enteringthe valve body 18 at port 33 while the return line is shown symbolicallyat port 34.

Valving mechanism in the form of a spool valve 35 having a spool 36riding in a multiported valve housing 37 is located within the valvebody 18 and, consequently, within the housing 10.

The spool valve housing 37 has means in the form of ports 38, 39 and 40for coupling the valve via passages or ducts in the valve body 18 to thepressure and return ports 33 and 34. For reasons to be explained belowthe spool 36 has a neutral closed position (see FIG. 1) and twooperative open positions. The valve spool is constructed with lands 41and 42 to occlude a first valve port 43 and a second valve port 44simultaneously in the neutral position, as shown. When the spool 36 isdisplaced downwardly as viewed in FIG. 1 the port 43 is brought intocommunication with the port 39 coupled to the return port 34 while theport 44 is opened to the pressure port 33 by way of valve port 38.Alternatively,

when the spool 36 moves upwardly from the neutral position the port 43is coupled to the pressure port 33 and the port 44 is coupled to thereturn port 34.

A symmetrical system of ducts in the form of fluid passages in the body18 are provided for coupling the actuator elements to the valvemechanism. Considering the cylinder 23 it is provided at opposite endswith fluid ports 45 and 46. If fluid under pressure is introducedthrough port 45 to the cylinder it will urge ram 21 toward the right asviewed in FIG. 1. This will urge the piston 11 outwardly of the housing10 thereby straining the elastic sheet 13 which, in addition to itsfunction of hydraulically sealing the housing, functions as a springtending to return the piston 11 toward the left to its neutral position.

If the fluid is now permitted to leave cylinder 23 through port 45 whilefluid under pressure is supplied to port 46 the ram 21 and piston 11will move to the left until the supply of pressure fluid stops. Assumingsuflicient flow the piston 11 will be drawn inwardly again strainingelastic sheet 13. For convenience, we can refer to movement of ram 21when pressure is supplied through port 45 as movement in a first modeand when pressure is supplied through port 46 as movement in a secondmode. Each of the other rams 22, 25 and 26 can be said to have similarmodes of operation. The corresponding cylinders each have a portassociated with each mode of operation. Thus, cylinder 24 has ports 47and 48, cylinder 27 has ports 49 and 50 and cylinder 28 has ports 51 and52.

Four passages, 53, 54, 55 and 56, all of equal length and diameter, jointhe respective ports 45 and 47 to a passage 57 and ports 49 and 51 to apassage 58. Again, the passages 57 and 58 should be of equal length anddiameter although the diameter may be larger than that of passages 53,54 55 and 56. The passages 57 and 58 merge in a passage 59 whichconnects with valve port 43.

In similar manner the ports 46, 48, 50 and 52 are coupled through fourpassages 60, 61, 62 and 63 to passages 64 and 65 which merge intopassage 66 coupled to valve port 44. The passages 60, 61, 62 and 63should all be equal in length and diameter. Passages 64 and 65,likewise, are made equal in length and diameter. Immediately, it shouldbe evident that perfect hydraulic symmetry exists between the actuatormeans coupled to piston 11 on the one hand and the actuator meanscoupled to piston 12 on the other hand. Furthermore, in the actualstructure shown in FIGS. 3 to 12 the lengths of the various passageswere chosen such that every port in the cylinders 23, 24, 27 and 28 wasthe same total distance from the corresponding valve port 43 or 44. Forexample, the total length of passages 53, 57, and 59 ,was made equal tothe total length of passages 62, 65 and 66.

The important factor is to construct the passages or ducts which couplethe valve mechanism to the actuator elements so as to obtainsubstantially identical fluid transfer characteristics between the spoolvalve and each of the actuator elements. This means that the pressuredrops, phase lags, and flow rates shall be substantially identical inthe hydraulic supply to each actuator element. It should also beunderstood that for eflicient operation the pressure drop should bemaintained at a minimum. This can be achieved by enlarging the diametersof the fluid passages. However, enlarging the size of the passagesincreases the compliance of the fluid which introduces serious phasedistortion. It is necessary to arrive at an arbitrary compromise. Apressure drop of about 50 p.s.i. proved satisfactory in the structurewhich was field tested.

An electrodynamic structure including a D.C. energized field 67 and avoice or signal coil 68 actuates or controls the spool 36 through anarmature 69 acting against the reaction of a resilient pad or cushion70. The armature 69 is resiliently supported in a neutral posit on byresilient supports 71 and 72. It will be understood that with no signalon the coil 68 the supports 71 and 72 maintain downward pressure on thespool 36 to keep pad 70 under compression. Thus, the pad is capable ofurging the spool in the upward direction when the control signal is suchas to move the armature 69 in that direction.

A drain system 73 is provided for returning all hydraulic fluid thatshould leak past the various seals to a return line 74. Finally, sincethe entire device is intended to operate well below the surface of abody of water, connections 75 and 76 are provided for supplying andexhausting air under pressure to and from the interior of housing 10.The internal pressure is maintained preferably fractionally higher thanthe external hydraulic head in order to ensure air leakage as opposed towater ingress in the event of a leak developing. At the same time thesystem is balanced dynamically so that power is required only forimparting acoustic energy to the surrounding medium.

Terminal 77 is provided for the various electrical connections requiredto energize and control the electrodynamic structure.

It has been mentioned that with zero signal on coil 68, the cushion 70is under compression. As shown in the drawings the electrodynamicstructure is constructed as a unit and installed in valve body 18 sothat armature 69 rests on the end of the valve spool 36. Initialadjustment of the position of spool 36 and the degree of compression ofcushion 70 is obtained by positioning the electrodynamic structure withthe threaded members 78, 79 and 80. (See FIGS. 3 and 8.) Member 78 isthreaded into the top of the electrodynamic structure for raising sameWhile members 79 and 80 are threaded into the top cover 81 joined to thevalve body for imparting downward movement. The structure is locked infinal position by set screws 82, 83 and 84.

By comparing FIGS. 3-12 with FIG. 1 it is possible to follow andunderstand all of the details of construction and operation, bearing inmind that the same reference numerals are used throughout to designatethe same or equivalent part.

Above there has been described what is presently considered thepreferred structure for embodying the invention. Nevertheless, numerouschanges will appear to those skilled in the art and it is to beunderstood that these are contemplated herein to the extent that they donot depart from the true spirit of the invention as defined in theappended claims.

What is claimed is:

1. An underwater sound source comprising:

a fluid tight housing having rigid wall portions including oppositelydirected sound-radiating pistons,

at least two hydraulic actuator means Within said housing coupledmechanically one to each of said pistons for imparting reciprocatorymotion thereto, means for obtaining hydraulic power, a central valvingmechanism within said housing, duct means freely inter-coupling saidactuator means in parallel, said duct means additionally coupling saidactuator means to said means for obtaining hydraulic power through saidcentral valving mechanism for operating the actuator means under thecontrol of said central valving mechanism, the duct means between saidcentral valving mechanism and said actuator means being dimensioned toprovide for hydraulic symmetry between the actuator means coupledrespectively to one and the other of said pistons,

spring means coupling each of said pistons to stationary portions ofsaid housing for biasing said pistons toward an intermediate position,

and means for controlling said central valving mechanism so as to causereciprocation of said pistons substantially in unison alternatelyoutwardly and inwardly relative to the interior of the housing therebyvarying the instantaneous volume of said housing.

2. An underwater sound source according to claim 1,

wherein said actuator means are each coupled by said duct means in aclosed hydraulic loop to said means for obtaining hydraulic power, withsaid central valving mechanism interposed at least between the pressureside of said means for obtaining hydraulic power and said actuatormeans.

3. An underwater sound source according to claim 2,

wherein said central valving mechanism is interposed between saidactuator means and both the pressure and return sides of said means forobtaining hydraulic power.

4. An underwater sound source comprising:

a fluid tight housing having rigid wall portions including oppositelydirected sound-radiating pistons,

a first group of one or more hydraulic actuator means within saidhousing coupled mechanically to one of said pistons for impartingreciprocatory motion thereto,

a second group of one or more hydraulic actuator means within saidhousing coupled mechanically to the other of said pistons for impartingreciprocatory motion thereto,

means for obtaining hydraulic power,

a unitary valve assembly within said housing coupling said means forobtaining hydraulic power through a network of fluid passages to saidtwo groups of actuator means in parallel and free inter-communicationfor operating the latter under the control of the valve assembly, thefluid passages being dimensioned to provide for hydraulic symmetrybetween the actuator means of said first and second groups,

spring means coupling each of said pistons to stationary portions ofsaid housing for biasing said pistons toward an intermediate position,

and means for controlling said valve assembly so as to causereciprocation of said pistons substantially in unison alternatelyoutwardly and inwardly relative to the interior of the housing therebyvarying the instantaneous volume of said housing.

5. An underwater sound source comprising:

a fluid tight housing having rigid wall portions including oppositelydirected sound-radiating pistons,

at least two rectilinear motion hydraulic actuator elements within saidhousing coupled mechanically one to each of said pistons for impartingrectilinear motion thereto, said elements each having a first mode ofoperation and an hydraulic fluid port associated with such mode,

a pressure and a return port for supplying hydraulic power,

a multi-ported spool valve within said housing constructed selectably toocclude or couple a first valve port alternatively with a second orthird valve port,

first duct means for coupling said second and third valve portsrespectively with said pressure and return ports,

second duct means inter-coupling between themselves and with said firstvalve port all of the fluid ports of said actuator elements which areassociated with said first mode of operation, said second duct meansbeing dimensioned to provide substantially identical fluid transfercharacteristics between said spool valve and each of the actuatorelements,

spring means coupling each of said pistons to stationary portions ofsaid housing for biasing said pistons toward an intermediate position,

and means for controlling said spool valve so as to cause reciprocationof said pistons substantially in unison alternately outwardly andinwardly relative to the interior of the housing thereby varying theinstantaneous volume of said housing.

6. An underwater sound source comprising:

a fluid tight housing having rigid wall portions including oppositelydirected sound-radiating pistons,

at least two rectilinear motion hydraulic actuator elernents within saidhousing coupled mechanically one to each of said pistons for impartingrectilinear motion thereto, said elements each having two modes ofoperation and one hydraulic fluid port associated with each mode,

pressure and a return port for supplying hydraulic power,

multi-ported spool valve within said housing including means forcoupling it to said pressure and return ports and having a neutralclosed position and two operative open positions, said valve beingconstructed to occlude a first and a second valve port simultaneously insaid neutral position and to couple said first and second valve ports insaid operative positions alternatively with said pressure and return orreturn and pressure ports respectively,

first duct means inter-coupling between themselves and with said firstvalve port all of the fluid ports of said actuator elements which areassociated with a first of said two modes of operation,

second duct means inter-coupling between themselves and with said secondvalve port all of the fluid ports of said actuator elements which areassociated with the second of said two modes of operation,

said first and second duct means being dimensioned to providesubstantially identical fiuid transfer characteristics between saidspool valve and each of the actuator elements,

spring means coupling each of said pistons to stationary portions ofsaid housing for biasing said pistons toward an intermediate position,

and means for controlling said spool valve so as to cause reciprocationof said pistons substantially in unison alternately outwardly andinwardly relative to the interior of the housing thereby varying theinstantaneous volume of said housing.

References Cited by the Examiner UNITED STATES PATENTS 2,172,066 9/1939Logsdon 116l37 3,056,104 9/1962 De Kanski et al 340--5 3,059,663 10/1962Whitenack 137-623 3,143,999 8/1964 Bouyoucos 340-8 X CHESTER L. JUSTUS,Primary Examiner.

LOUIS J. CAPOZI, LEWIS H. MYERS, Examiners.

G. M. FISHER, Assistant Examiner.

1. AN UNDERWATER SOUND SOURCE COMPRISING: A FLUID TIGHT HOUSING HAVINGRIGID WALL PORTIONS INCLUDING OPPOSITELY DIRECTED SOUND-RADIATINGPISTONS, AT LEAST TWO HYDRAULIC ACTUATOR MEANS WITHIN SAID HOUSINGCOUPLED MECHANICALLY ONE TO EACH OF SAID PISTONS FOR IMPARTINGRECIPROCATORY MOTIONS THERETO, MEANS FOR OBTAINING HYDRAULIC POWER, ACENTRAL VALVING MECHANISM WITHIN SAID HOUSING, DUCT MEANS FREELYINTER-COUPLING SAID ACTUATOR MEANS IN PARALLEL, SAID DUCT MEANSADDITIONALLY COUPLING SAID ACTUATOR MEANS TO SAID MEANS FOR OBTAININGHYDRAULIC POWER THROUGH SAID CENTRAL VALVING MECHANISM FOR OPERATING THEACTUATOR MEANS UNDER THE CONTROL OF SAID CENTRAL VALVING MECHANISM, THEDUCT MEANS BETWEEN SAID CENTRAL VALVING MECHANISM AND SAID ACTUATORMEANS BEING DIMENSIONED TO PROVIDE FOR HYDRAULIC SYMMETRY BETWEEN THEACTUATOR MEANS COUPLED RESPECTIVELY TO ONE AND THE OTHER OF SAIDPISTONS, SPRING MEANS COUPLING EACH OF SAID PISTONS TO STATIONARYPORTIONS OF SAID HOUSING FOR BIASING SAID PISTONS TOWARD AN INTERMEDIATEPOSITION, AND MEANS FOR CONTROLLING SAID CENTRAL VALVING MECHANISM SO ASTO CAUSE RECIPORCATION OF SAID PISTONS SUBSTANTIALLY IN UNISONALTERNATELY OUTWARDLY AND INWARDLY RELATIVE TO THE INTERIOR OF THEHOUSING THEREBY VARYING THE INSTANTANEOUS VOLUME OF SAID HOUSING.